1. Field of the Invention
This invention relates to a wireless communication system and to a method of making the system. More particularly, the invention relates to a wireless communication system, such as for portable telephones, on a chip.
2. Discussion of the Related Art
Emerging applications for portable wireless voice and data communications (wireless internet) systems require increased data rates and functionality. Meeting cost and performance goals requires careful attention to system level design and partitioning such that appropriate technologies are employed in cost-effective implementations. It is believed that optimum implementations will employ a mixture of GaAs and silicon integrated circuits as well as high-performance miniaturized passive components.
As the existing RF spectrum becomes more and more crowded, new radio frequency integrated circuit (RFIC) capabilities will be required to implement power and spectrally efficient digital modulation and demodulation schemes needed by new wireless systems.
Typical radio architectures and transceiver sub-circuits which have been integrated are described by L. M. Burns, “Applications for GaAs and Silicon ICs in Next Generation Wireless Communication-Systems,” Technical Digest, 16th Annual GaAs IC Symposium, p. 155-158, 1994, which publication is incorporated herein by reference.
A circuit from the Burns et al publication is provided in FIG. 1. With reference to FIG. 1, there is shown Plessey's Frequency Hopping Spread Spectrum transceiver, which operates in the 2.4 GHz GSM band, and which is a good example of a wireless system for use with the present invention. The system has a base double conversion super heterodyne architecture with only two master oscillators which enables fast switching between transmit and receive modes. GaAs is used in the IC 20 containing the low noise amplifier (LNA), up and down converting mixers, switches for transmit/receive (T/R) and antenna switching 22 and one of the voltage controlled oscillators (VCO's) 23. The second IC 30 contains the downconverting mixer, intermediate frequency (IF) limiting amplifier, received signal strength indicator (RSSI) and frequency discriminator. This IC 30 is fabricated using a high speed silicon bipolar process.
A third IC 40, fabricated using the same high speed silicon bipolar process, contains high frequency prescalers, dividers and the second VCO. Three phase locked loops (PLLs) 50, 52, 54 fabricated in 1 μm CMOS are used to set the frequencies of the two master oscillators. A variety of miniature, high performance passive filters are also used. A high-Q ceramic resonator filter is used to band limit the transmit/receive (TX/RX) signals. Surface acoustic wave (SAW) filters are used in the first and second IF strips to provide needed selectivity while maintaining good group delay characteristics. A simple gaussian LC lowpass filter is used to pulse shape the transmitted signal to implement GFSK modulation.
Another RF transmission/reception circuit from the Burns et al. publication which has been integrated is shown in FIG. 2. With reference to FIG. 2, the wireless system shown is the National Semiconductor DECT transceiver. This transceiver contains many of the same functional building blocks as the Plessey example in FIG. 1. The transceiver operates in the 1.88-1.90 GHz band. Almost all of the ICs in this design are fabricated in National's silicon BiCMOS IC process. The most notable exception is the GaAs power amplifier. Although the silicon downconverter/mixer has a relatively high aggregate noise figure of 8.7 dB, this is adequate to meet DECT specifications. A single conversion, superheterodyne receiver is used. The DECT transceiver also uses gaussian filtering on the transmitted data stream. However, the National transceiver filters the bit stream with an on-chip gaussian lowpass filter based on a ROM look-up table.
Optical transceiver applications have also been integrated. See, for example, Rodrigo et al, “AlGaAs/GaAs HEMT 5-12 GHz Integrated System for an Optical Receiver,” Proceedings of the 1998 IEEE International Symposium on Circuits and Systems, vol. 2, p. 312-315, 1998, which publication is incorporated herein by reference. A system from Rodrigo et al is illustrated in FIG. 3. The circuit includes an input network 80 to emulate the photodiode function, a pre-amplifier 82, an automatic gain control (AGC) unit 84, two gain stages 86, the comparator 87 and the output buffer 88.
Microwave transmission and reception circuits have also been integrated. There are two basic types of integrated circuit structures for microwave transmission/reception systems: monolithic microwave integrated circuits (MMIC) and microwave integrated circuits (MIC). However, these structures have basic problems. The MMIC die is large because needed microwave matching and filter circuits occupy a large area which results in high cost. The MIC die is also large because conventional MIC's consist of single-layer circuits. In response to these problems, a multilayer microwave integrated circuit (MuMIC) was introduced by Matsushita Electronics as described by N. Yoshikawa et al in “Multilayer Microwave Integrated circuit Technology for GaAs Power Amplifier of Personal Communication System,” Technical Digest of 1995 International Solid State Circuit Conference, p. 190-191, 365, 1995, which publication is incorporated herein by reference. The MuMIC uses a multilayer substrate formed of low temperature co-fired ceramics.
To reduce the size and weight of mobile telephones, tape automated bonding (TAB) has been used in a multilayer integrated circuit configuration to assemble a 900 MHz-band GaAs multichip power amplifier module for a Mitsubishi Electric transmitter as described in Y. Notani et al, “GaAs Multi-chip Power Amplifier Module using a Multi-layer TAB Tape,” Technical Digest, 1994 16th Annual GaAs IC symposium, p. 145-148, 1994, which publication is incorporated herein by reference.
Another example of a radio frequency integrated circuit (RFIC) is described by McGrath et al in “A 1.9 GHz GaAs Chip Set for the Personal Handyphone System,” IEEE Transactions on Microwave Theory and Techniques, vol. 43, no. 7, p. 1733-1744, 1995, which publication is incorporated herein by reference. The McGrath et al publication includes chip, partition, design and performance of each sub-function relative to requirements imposed by an air interface.
Although the articles discussed above illustrate attempts at integrating many of the components of a wireless communication system using several ICs and passive components, they still require numerous integrated circuits and/or large die areas. Accordingly, further integration and size reduction is required, particularly for wireless communications devices, such as cellular telephones.